Seeing Beyond the Big Bang

byPaul GilsteronDecember 22, 2008

“It’s no longer completely crazy to ask what happened before the Big Bang,” says Caltech’s Marc Kamionkowski. A good thing, too, for this is an absorbing subject, one I’ve been interested in ever since reading Poul Anderson’s 1971 novel Tau Zero, in which the crew of the runaway starship Leonora Christine punches through into another universe. That novel assumed a cyclic universe, a collapse and a rebound, naturally making one ask whether a universe hadn’t existed before our own. If so, could we learn anything about it?

I would always have assumed the answer is no, but Kamionkowski’s work, and that of collaborators Adrienne Erickcek and Sean Carroll, at least opens the possibility that we might see an ‘imprint’ of that earlier universe in data we can collect today. The work grows out of measurements of the cosmic microwave background (CMB), as examined by the Wilkinson Microwave Anisotropy Probe. Temperature differences in the CMB can be used to study the theory of inflation, the idea that the universe went through a dramatic expansion immediately after the Big Bang, which would explain why it appears identical in all directions.

The problem is that the CMB isn’t as uniform as once thought. The Big Bang’s afterglow is more mottled in one half of the sky than the other. Exploring an energy field called the curvaton, which had been proposed to explain CMB fluctuations, Kamionkowski’s team tweaked the field so that its effects would more adequately explain the temperature variations. This theoretical tweak is, fortunately, subject to testing by the Planck satellite, which will launch in 2009. Says Erickcek:

“Inflation is a description of how the universe expanded. Its predictions have been verified, but what drove it and how long did it last? This is a way to look at what happened during inflation, which has a lot of blanks waiting to be filled in.”

Looking at the inflation era is itself extraordinary, but there is also the possibility that the perturbation the scientists introduced into the inflation picture is an imprint from whatever came before inflation. This is heady stuff, but it’s clear that Kamionkowski isn’t alone in thinking that we can perhaps glimpse some of these early mechanisms.

For a new paper by Jean-Luc Lehners and Paul Steinhardt (both at Princeton) looks first at cyclic universe models in which the universe undergoes periods of expansion and contraction, with a big crunch followed by a big bang marking the transition between the two, and then goes on to posit a ‘phoenix universe’ in which a tiny part of the universe survives the cataclysmic cycling but manages to become the basis for everything in the next universe. Steinhardt has been a major player in so-called ‘ekpyrotic universe’ models (a term meaning ‘out of the fire’), which offer alternatives to standard inflation.

Intriguingly, Lehners and Steinhardt see a role for dark energy in managing the survival of at least some of the earlier universe. This is dense and challenging reading, but the paper is well worth your time in its examination of this transformative process. A snippet:

…without adding some mechanism to force the universe to begin very close to the classical track, an overwhelming fraction of the universe fails to make it all the down the classical trajectory simply due to quantum ﬂuctuations. This fraction is transformed into highly inhomogeneous remnants and black holes that do not cycle or grow in the post-big bang phase. However, …something curious happens if the dark energy expansion phase preceding the ekpyrotic contraction phase lasts at least 600 billion years. Then, a sufficiently large patch of space makes it all the way down the classical trajectory and through the big bang such that, fourteen billion years later, it comprises the overwhelming majority of space. This surviving volume, which grows in absolute size from cycle to cycle, consists of a smooth, ﬂat, expanding space with nearly scale-invariant curvature perturbations, in accordance with what is observed today. As with the mythical phoenix, a new habitable universe grows from the ashes of the old.

A third way of poking into the early universe is Abhay Ashtekar’s work on a recycled universe that can be explained through loop quantum cosmology (LQC), a universe that works its way through an eternal series of expansions and contractions. New Scientist wrote this up in a recent article, examining the notion that space itself comes in the form of indivisible quanta 10-35 square meters in size. Martin Bojowald, working with Ashtekar at Penn State, used loop quantum gravity to create a model of the universe that has been the subject of much modification ever since. A singularity-free universe results, one in which universal collapse is reversed and the infinitely dense singularity disappears:

If LQC turns out to be right, our universe emerged from a pre-existing universe that had been expanding before contracting due to gravity. As all the matter squeezed into a microscopic volume, this universe approached the so-called Planck density, 5.1 × 1096 kilograms per cubic metre. At this stage, it stopped contracting and rebounded, giving us our universe.

The Planck density itself cannot be reached, as the New Scientist story goes on to explain:

According to Bojowald, that is because an extraordinary repulsive force develops in the fabric of space-time at densities equivalent to compressing a trillion solar masses down to the size of a proton. At this point, the quanta of space-time cannot be squeezed any further. The compressed space-time reacts by exerting an outward force strong enough to repulse gravity. This momentary act of repulsion causes the universe to rebound. From then on, the universe keeps expanding because of the inertia of the big bounce. Nothing can slow it down – except gravity.

How far we have to go in all this, but what fascination in the attempt! The mind sometimes boggles, but Anil Ananthaswamy’s article in New Scientist is a major help at untangling what Ashtekar is doing. Caltech offers a helpful news release on Kamionkowski’s work on asymmetry in the early universe; the paper itself (abstract here) is Kamionkowski et al., “A hemispherical power asymmetry from inflation,” Physical Review D Vol. 78, Issue 12 (16 December 2008). Lehners’ and Steinhardt’s paper is “Dark Energy and the Return of the Phoenix Universe,” available online.

Comments on this entry are closed.

Frank SmithDecember 22, 2008, 14:27

Loved Anderson’s novel, but I could not figure out how the Leonora Christine was exempt from the Big Crunch. No matter how big the Tau got, the Leonora Christine should have been in the same space-time bubble as everything else, and thus crunched when the rest of the universe was.

But in the story, they got to watch the bounce and then they were back in bubble to take part in the new universe.

For those without subscriptions, a pre-print of “A Hemispherical Power Asymmetry from Inflation” is available at “arXiv:0806.0377v1 [astro-ph] 3 Jun 2008”. Peter Lynds offers an interesting take on the cyclical universe in “On a Finite Universe with no Beginning or End “: unfortunately I’ve lost the link to that paper but you may be able to access in through the FQXi web site.

Also, I have thought about some kind of experiment that a very very distant future human or a distant future ETI civilization might undertake that would somehow involve the acceleration of say an electron to a relativistic kinetic energy equal to 10 EXP 39 Kilograms/(C EXP 2) and crash it head on into a similar electron traveling in the opposite direction with the same kinetic energy. It would seem that such tremendously relativistic electrons would take the form of black holes, but if the blackholes could be aligned so that the central singularities collide, perhaps densities much greater, perhaps many orders of magnitude greater than the Planck Density could be achieved, although perhaps at the risk of scrambling that nature and integrity of cause and effect within the our universe if not any entire existent multiverse.

The above conjecture might simply be a reification based on asking the wrong type of question, however, I am curious as to what human and/or ETI civilizations might be able to accomplish given 10 EXP 15 to 10 EXP 20 years of continued technological progress.

Perhaps there exist some sort of sub-singularity density state that could be made manifest upon the collision of such relativistic fundamental particles. However, it might be the case that space time fluctuations within the proximity of the impinging blackholes as such would smear out or force a density dilution thus preventing such extreme super Planck Density states from arising. If such density dilutions could be controlled by some sort of Planck level space time control or self-assembly type of technology, perhaps the dilution problem could be over come. In the event that a method could be devised to reach such super Planck densities, it might be unwise to do such except in casually and thermodynamically decoupled universe. But man, what a collider experiment any such technology might permit.

Regardless, the studying of extreme states that are obtainable by nature may offer us humans a means to technologically surpass these states. An analogy I present is the construction of a small fusion reactor that might process fusionable isotopes for electrical power indefinitely or virtually so wherein nature seems to have only produced long duration nuclear fusion reactors in the form of single units with the mass of and the form of stars.

The hemispherical asymmetry is very curious. Has people talking of a “curvaton” to add to the “inflaton” – neither field has actually been observed in any local level physics, so a dash of scepticism is needed. Yet wouldn’t it be amazing to see “New Physics” arise out of this conundrums? Perhaps the LHC will pin down SUSY or SUGRA or some such – or utterly disconfirm them – and give us some more hints as to what is really going on.

John Maddox, editor of “Nature”, asked “What remains to be discovered?” in one of his books. Seems physics might have a few more surprises for us yet…

Many views on the Origin of Universe are available. Most popular view is that universe was born with a big-bang from a highgly dense energy point. But I have some different view on it. I think the universe was not born from a concentrated point or ball like structure but it has evolved from an infinite vast expanse of field of gravity. Philosophically or religously we may call it field of consciousness or spirituality.

A great flow of current of gravitation force descended down from this source and has created many regions of pure gravitation force below it. This was the creation for quite some time in the first phase of the creational process. In the second phase when the current of gravitation force further descended down then electromagnetic forces and matter (weak and strong nuclear forces)manifested and the entire universe of the second phase was completed with the admixture of all the forces viz., gravitatin force, electromagnetic forces, and matter (weak and strong nuclear forces. The completion of the whole cosmos in two phases was also hinted in one of the speeches of Prof. J.V.Narlikar some years back. When the process of creation of universe reverts back in Brahmand (universe created during second phase of creational process)the matter merges into electromagnetic force and then finally electromagnetic forces merge into gravitation force and nothing remains except field of gravity in a highly dense body (Black Hole. The process of reversal does not take place in the universe created during first phase of creation. The cycle of universe completes like this.

Many philosophical-scientific evidences can be quoted in support of this assumption
.

See also the excellent book “Cities in flight” by James Blish in which the final volume deals with exactly the end and rebirth of a cyclical matter/antimatter-universe, and how the protagonists attempt to affect the outcome of the next universe by their actions.

Abstract: Certain results of observational cosmology cast critical doubt on the foundations of standard cosmology but leave most cosmologists untroubled. Alternative cosmological models that differ from the Big Bang have been published and defended by heterodox scientists; however, most cosmologists do not heed these. This may be because standard theory is correct and all other ideas and criticisms are incorrect, but it is also to a great extent due to sociological phenomena such as the “snowball effect” or “groupthink”. We might wonder whether cosmology, the study of the Universe as a whole, is a science like other branches of physics or just a dominant ideology.

Abstract: In this paper we compare the existing observational data on type Ia Supernovae with the theoretical evolutions of the universe predicted by a one-parameter family of tachyon models which we have introduced recently in paper [6].

Among the set of the trajectories of the model which are compatible with the data there is a consistent subset for which the fate of the universe ends up in a new type of soft cosmological singularity dubbed Big Brake. This opens up yet another scenario for the future history of the universe besides the one predicted by the standard $\Lambda$CDM model.

If our Universe once collided with another, we might soon be able to see the evidence in the distant reaches of the cosmos, say astrophysicists

As far as we can tell, the universe is about 93 billion light years big and about 14 billion years old.

That’s a head scratcher for cosmologists. In 14 billion years, light can travel…errr…14 billion light years. So how did the universe get so big, so quickly?

The best explanation is a mysterious process called inflation. The general idea is that soon after it was born, the universe rapidly increased its size by many orders of magnitude in an instant.

Cosmologist love to ponder the way in which inflation was triggered. Short answer: nobody really knows, although there’s no shortage of speculation.

A somewhat lesser known problem is what might have stopped inflation. Why doesn’t the cosmos continue to expand at an exponential rate?

One of the most curious answers is this: that the universe is still expanding and that we exist in a tiny region of stability, a cosmic bubble in a mighty maelstrom.

Of course, our cosmic bubble would be just one among countless others.

But how could we ever see these other bubbles given that they must be beyond the edge of the visible universe?

Today, Anthony Aguirre at the University of California, Santa Cruz and his buddy Matthew Johnson at Caltech review this scenario and give an answer of sorts.

They say the only way that we could see evidence of another cosmic bubble is if it had collided with our universe in the distant past.

Interesting idea but not one without a few challenges. The main problem is that in mosts cases collisions would destroy the spacetimes in both bubbles, thereby ensuring that we couldn’t be here to observe the aftermath.

However, Aguirre and Johnson identify a class of cosmic collisions that preserve the three dimensions of space and one of time that we need for our existence. These are not so much cosmic collisions as glancing blows.

So what would the aftermath of such a cosmic scrape? Aguirre and Johnson say that evidence of a negative curvature to the universe we be compatible with the idea that we exist in a cosmic bubble while positive curvature would rule it out.

Beyond that, a cosmic prang would have left its mark in the form of various symmetric features in the cosmic microwave background.That’s something we could see in the data from telescopes such as Planck.

All tantalising stuff. But the trouble is that none of this would provide definitive, unambiguous evidence of a collision and that means we’ll probably never know for sure.

But cosmologists are not to be deterred, this is the kind of speculation they love.

Aguirre and Johnson finish with this statement:

“With some luck, the discovery of ‘other universes’, a concept seemingly out of science fiction, may be just around the corner!”

If you believe that, you have a fruitful career ahead of you in cosmology

IS OUR universe a recycled version of an earlier cosmos? The idea, which replaces the big bang with a “big bounce”, has received a boost: this vision of the birth of the universe can explain why a subsequent process, called inflation, occurred.

“The result puts the idea of inflation on firmer ground, and at the same time makes the bounce scenario much more credible,” says Carlo Rovelli, who was not involved in the work but studies quantum gravity at the University of Marseille in France.

Physicists have simulated two universes colliding inside a metamaterial

kfc 01/30/2012

One interesting way in which our cosmos may have formed is in a collision between two other universes with extra spatial dimensions called braneworlds.

In this scenario, known as the ekpyrotic model of the universe, our cosmos is just a small four-dimensional corner of a much more complex space.

The ekpyrotic model is interesting because it leads to a flat universe like our own without the need for inflation, the period just after the Big Bang in which our universe supposedly swelled by many orders of magnitude in the blink of an eye.

Without inflation, our universe is just too big to have been formed in a Big Bang-type event. But nobody knows what might cause such a dramatic increase in size. Hence the interest in another way of explaining our existence.

If you’re wondering what actually collides in the ekpyrotic version of events, the answer is Minkowski domain walls, essentially the edges of universes with different spatial dimensions.

It’s easy to imagine that Minkowski domain walls are entirely theoretical. And indeed they were until now.

Today, Igor Smolyaninov and Yu-Ju Hung at the University of Maryland, in College Park, say they’ve created Minkowski domain walls in the lab for the first time and even used them to simulate the collision of two braneworlds.

The trick these guys have used is a formal analogy between the mathematics of space time and of electromagnetic spaces. Physicists have known since Einstein’s day that it is possible to bend and distort the fabric of spacetime—our universe appears to be distorted in just this way on various cosmic scales.

But it is only in the last ten years or so that they’ve learnt how to do the same on a much smaller scale with electromagnetic spaces. What’s triggered this is the development of metamaterials: artificial substances that can bend light in almost any way imaginable.

Smolyaninov is fascinated by one version of this stuff called hyperbolic metamaterial. Inside this substance, monochromatic light propagates in a similar way to massive particles in a Minkowski spacetime, where one spatial coordinate takes on the role of time.

Hyperbolic metamaterials are essentially a series of metal layers separated by a dielectric. Smolyaninov has used this stuff to simulate a number of interesting aspects of cosmology including the Big Bang itself.

The collision between universe’s is a variation on this theme. “The “colliding universe” scenario can be realized as a simple extension of our earlier experiments simulating the spacetime geometry in the vicinity of big bang,” he says.

He simulates an expanding universe using concetric rings of gold separated by a dielectric. “When the two concentric ring (“universe”) patterns touch each other (“collide”), a Minkowski domain wall is created, in which the metallic stripes touch each other at a small angle,” he says.

Being able to recreate these exotic events in the lab is certainly interesting but it is beginning to lose its novelty. The problem is that this work is not telling us anything we didn’t know–the universe behaves the same way inside a metamaterial as it does outside.

What Smolyaninov needs is a way of using his exotic materials to do something interesting. In other words, he needs a killer app. Any ideas?

A simple, yet mind bending, question in cosmology is to ask what took place before the Big Bang. Jeff Foust reviews a book that examines the concept of time, both in a cosmological context as well as how humanity’s perception and measurement of time has altered over the millennia.

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last twelve years, this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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